Last year Microsoft was promising great advances in the way we use computers thanks to Vista, a new version of its Windows system. Just 18 months later, however - and after a barrage of criticism - the company yesterday unveiled its successor, Windows 7.

The new system, which is unlikely to go on sale for at least a year, attempts to fix a number of problems with Vista and allow Microsoft to compete with a new generation of internet-based systems that are beginning to challenge its worldwide dominance.

Showing off Windows 7 for the first time at a conference in Los Angeles, Microsoft's chief software architect, Ray Ozzie, unveiled a vision of the future that took in mobile phones and the web as well as ordinary desktop PCs. "We are bringing the best of the web to Windows, and the best of Windows to the web," said Ozzie, who took over the company's strategy from co-founder Bill Gates.

At first glance, Windows 7 appears similar to Vista, but Microsoft promises a number of improvements. The system will be faster and easier to use, said Ozzie, and is set to include hi-tech bells and whistles such as support for a new generation of multitouch screens similar to Apple's iPhone.

Ozzie also demonstrated a version of Microsoft Office that uses the internet to store files, allowing users to pick up their documents from any online computer.

"We've done a lot of work around how you manage the windows, how you launch programs and how you manage the windows of the programs you've launched," said Steven Sinofsky, senior vice president for Windows.

However, it remains to be seen whether Windows 7 can erase the memory of Vista, which has proved one of the most difficult product launches in the history of the Seattle-based software company.

Initially trumpeted as the most important product of the decade, Vista fell behind schedule and eventually received a lukewarm reception from users. The lack of momentum has left Microsoft struggling while rivals such as Google and Apple have made significant advances.